In Hesiod’s myth of Pandora, evils escaped into the world when she opened the vessel.
In Works and Days, Zeus has Pandora sent to humanity, and she opens a sealed container after receiving it. The contents rush out and spread suffering among human beings. Hesiod describes the released contents broadly as evils, including troubles and diseases, rather than presenting the familiar modern image of one specific monster or object.
The story’s best-known detail is that Hope remains inside after Pandora closes the vessel. That detail has generated centuries of debate: some readers interpret Hope as a comfort preserved for humanity, while others note that Hesiod’s wording leaves its exact role open to interpretation.
The phrase “Pandora’s box” is itself a later misunderstanding. Hesiod used the Greek word pithos, meaning a large storage jar or vessel. Renaissance scholarship helped popularize the box wording, which is now much more familiar in English than the original jar.